Ann Brennan was born in Wandin Valley but when she was 10 years old she and her mother moved to Perth after her mother discovered that Snow was in love with another woman. They had very little contact with Snow after that and relations were very strained. She was very surprised when Snow left his farm (in March 1990) to both Ann and her younger half-sister, Steve, who had been born after Ann and her mother had left. Ann originally wanted to sell the farm, split the proceeds with Steve, and return to her life in Perth. When she learned that her married lover, Peter Kerr (a surgeon), had gotten his wife pregnant (when they were supposedly not even sleeping together) she decided to stay in the Valley for awhile.

She took on the job of Director of Nursing at the hospital and eventually sold her flat in Perth so that she could invest money in the farm and settle permanently in the Valley. The relationship between her and Steve was very strained at first -- Steve resented the fact that Ann and her mother had abandoned Snow and not kept in touch. When she was a little girl, just before she and her mother had left the farm, Ann buried a time capsule in one of the fields. Steve unearthed the tin canister years later and the contents gave her insight into what her sister was like as a child. They later reburied it but their relationship was much better from that point on, in spite of the fact that they were very different in personality and habits. Ann was a vegetarian and a smoker and not overly fond of Steve's cat, Lionel.

She and Dr. Cris Kouros were interested in each other from the start but it wasn't until Cris's daughter Jessie set them up (by tricking them into a dinner date) that they began to really date. They fell in love and, after the self-induced death of a cancer patient tarnished Cris's reputation, they moved to Melbourne with Jessie in March 1991. In Melbourne, Ann was supervisor of a young nurse named Kate Bryant who eventually moved to the Valley herself. Shortly after Kate arrived and while preparing for a trip to Greece with her sister Ann and Cris Kouros in July 1991, Steve Brennan was killed in a fall off a horse, and Ann was devastated.